Abstract

VIVEROS-CONTRERAS, R. et al. Encapsulation of ascorbic acid into calcium alginate matrices through coacervation coupled to freeze-drying. Rev. Mex. Ing. Quím [online]. 2013, vol.12, n.1, pp.29-39. ISSN 1665-2738.

The aim of this work was to study the stability of ascorbic acid (AA) after encapsulation into calcium alginate matrixes by coacervation through: a) falling drop by dipping; AA-sodium alginate solutions into CaCl₂ solutions (IAA method), and by atomizing the AA-sodium alginate solutions into CaCl₂ solutions (SAA method), followed by freeze-drying of the obtained capsules. Sorption isotherms for both types of products were determined at the water activity (a_w) range of 0.103-0.892, at 15, 25 and 35^oC, by using the gravimetric method with saturated salt. The percentage of retention of AA was determined, after 15, 30, 45 and 60 days of storage at 25^oC. SEM micrographs of the products were obtained and the volume of micropores was also calculated. The minimum integral entropy of the water molecules occurred at a_w = 0.234 in the falling drop method powders, whereas this parameter was observed at a_w = 0.706 for the atomised one. For both types of products, the maximum value of AA retention was observed at the a_w corresponding to the minimum integral entropy which occurred at higher moisture contents for SAA than for IAA materials.

Keywords : ascorbic acid; encapsulation; minimum integral entropy; water sorption; storage lability.